Hydrothermal impacts on trace element and isotope ocean biogeochemistry

Hydrothermal activity occurs in all ocean basins, releasing high concentrations of key trace elements and isotopes (TEIs) into the oceans. Importantly, the calculated rate of entrainment of the entire ocean volume through turbulently mixing buoyant hydrothermal plumes is so vigorous as to be comparable to that of deep-ocean thermohaline circulation. Consequently, biogeochemical processes active within deep-ocean hydrothermal plumes have long been known to have the potential to impact global-scale biogeochemical cycles. More recently, new results from GEOTRACES have revealed that plumes rich in dissolved Fe, an important micronutrient that is limiting to productivity in some areas, are widespread above mid-ocean ridges and extend out into the deep-ocean interior. While Fe is only one element among the full suite of TEIs of interest to GEOTRACES, these preliminary results are important because they illustrate how inputs from seafloor venting might impact the global biogeochemical budgets of many other TEIs. To determine the global impact of seafloor venting, however, requires two key questions to be addressed: (i) What processes are active close to vent sites that regulate the initial high-temperature hydrothermal fluxes for the full suite of TEIs that are dispersed through non-buoyant hydrothermal plumes? (ii) How do those processes vary, globally, in response to changing geologic settings at the seafloor and/or the geochemistry of the overlying ocean water? In this paper, we review key findings from recent work in this realm, highlight a series of key hypotheses arising from that research and propose a series of new GEOTRACES modelling, section and process studies that could be implemented, nationally and internationally, to address these issues.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.

Role of the striatum and nucleus accumbens in paced copulatory behavior in the female rat

Female rats engage in a series of approach and avoidance behaviors (pacing behavior) directed at the male in order to achieve a preferred rate of intromissions that make pregnancy more likely to occur with insemination. The striatum and nucleus accumbens have been implicated in the modulation of pacing behavior. It is unclear, however, whether these areas of the brain are necessary for the display of pacing behavior. To address this question, ovariectomized female rats received either bilateral quinolinic acid lesions of the striatum or nucleus accumbens or sham surgeries. After hormone priming, rats were allowed to engage in mating behaviors in an apparatus in which they could pace the rate of the copulatory bout. There was a significant reduction in pacing efficiency after striatal lesions, in that females were less likely to leave the male's side of the chamber after a contact. Animals with lesions of the nucleus accumbens that included the shell were more likely to avoid sexual interaction altogether than animals with control lesions. Therefore, it is concluded that the striatum and nucleus accumbens modulate specific aspects of pacing behavior in the female rat.

The role of dopamine in the nucleus accumbens and striatum during sexual behavior in the female rat

Dopamine in dialysate from the nucleus accumbens (NAcc) increases during sexual and feeding behavior and after administration of drugs of abuse, even those that do not directly activate dopaminergic systems (e.g., morphine or nicotine). These findings and others have led to hypotheses that propose that dopamine is rewarding, predicts that reinforcement will occur, or attributes incentive salience. Examining increases in dopamine in NAcc or striatum during sexual behavior in female rats provides a unique situation to study these relations. This is because, for the female rat, sexual behavior is associated with an increase in NAcc dopamine and conditioned place preference only under certain testing conditions. This experiment was conducted to determine what factors are important for the increase in dopamine in dialysate from NAcc and striatum during sexual behavior in female rats. The factors considered were the number of contacts by the male, the timing of contacts by the male, or the ability of the female to control contacts by the male. The results indicate that increased NAcc dopamine is dependent on the timing of copulatory stimuli, independent of whether the female rat is actively engaged in regulating this timing. For the striatum, the timing of copulatory behavior influences the magnitude of the increase in dopamine in dialysate, but other factors are also involved. We conclude that increased extracellular dopamine in the NAcc and striatum conveys qualitative or interpretive information about the rewarding value of stimuli. Sexual behavior in the female rat is proposed as a model to determine the role of dopamine in motivated behavior.

Critical periods for the effects of alcohol exposure on brain weight, body weight, activity and investigation

Using an animal model of fetal alcohol syndrome - which equates peak blood alcohol concentrations across different developmental periods - critical periods for the effect of alcohol on brain weight, activity and investigative behavior were examined. The periods of alcohol exposure were from gestational day (GD) 1 through 10, GD 11 through 22, postnatal day (PD) 2 through 10, or all three periods combined. The critical period of alcohol exposure for an increase in activity in juveniles was GD 11 through 22. This pattern was not seen in the same animals in adulthood; instead, increases in both activity and investigation were seen in animals exposed from PD 2 through 10 and not seen in animals exposed during all three periods combined. Brain weight was reduced by alcohol exposure from GD 11 through 22, PD 2 through 10 and all three periods combined. The period from PD 2 through 10 was the only period when the brain weight to body weight ratio was reduced. In conclusion, exposure to alcohol during the periods in the latter half of gestation or early postnatal period seem to have the most deleterious effects on the brain, activity and investigation in the rat. In addition, the effects of alcohol exposure over both the prenatal and postnatal period cannot be easily predicted from the effects of shorter periods of exposure.

A preliminary study of hepatitis B virus replication during short-term (7-day) social drinking

The purpose of this study is to determine the effect of short-term social drinking on hepatitis B virus (HBV) replication as measured by serum levels of hepatitis B virus DNA (HBV-DNA). We studied five male carriers of hepatitis B e antigen who were social drinkers. Levels of HBV-DNA, blood alcohol, and aspartate aminotransferase (AST) were measured during abstinence from alcohol, before and during a test dose (29.8 g) of alcohol which followed one week of abstinence, and before and during the same test dose which followed social drinking for one week. We observed no significant changes in HBV-DNA or AST levels. These data suggest that a single one-week period of social drinking in patients with chronic HBV infection does not cause enhanced viral replication. The risks of repeated ingestion of moderate amounts of alcohol by such patients have not been established. Interpretation of our data is limited by the small number of subjects, and further studies are needed. Nevertheless, our results are consistent with published recommendations that social drinking by nonalcoholic HBV carriers should be restricted but need not be totally forbidden.

Effect of chronic ethanol ingestion on enterocyte turnover in rat small intestine

Whether chronic ethanol ingestion significantly damages the small intestine remains controversial. To clarify this we have analysed the morphology of the small intestinal epithelium and quantified its renewal in chronically ethanol fed rats. Twenty adult male rats were pair fed for 28 days a nutritionally adequate liquid diet containing either ethanol as 36% of total calories or an isocaloric diet in which fat substituted for ethanol. Crypt cell production rate was determined in the jejunum and ileum by the metaphase arrest method. Weight gain and small intestinal morphology were similar in ethanol fed and control rats, but enterocyte turnover was significantly reduced in the jejunum (p less than 0.05) and ileum (p less than 0.01) of the ethanol fed rats. This effect of ethanol on the small intestine is probably systemic rather than local, because the changes in jejunum and ileum were similar, and it may contribute to the development of malnutrition in chronic alcoholics.

Effect of chronic ethanol intake on lactase activity and active galactose absorption in rat small intestine

The effects of feeding a nutritionally adequate liquid diet containing 5% ethanol to rats over a four week period on intestinal lactase activity and the kinetics of jejunal galactose absorption in vivo have been determined. Both lactase activity and the maximum capacity for active, saturable galactose absorption (Jmax) were increased significantly after chronic ethanol ingestion. In contrast, uptake of the sugar via the phlorhizin-insensitive (passive) route was unaffected by ethanol. Our results imply the presence of an increased maturity of the enterocyte population on the villus surface in response to ethanol. The relevance of this work to uptake studies in alcoholics is briefly discussed.

Platelet function defects in chronic alcoholism

Platelet function in alcoholic patients was assessed on admission and during abstinence in hospital. On admission platelets from these patients were significantly less responsive (percentage aggregation and thromboxane A2 release) to conventional in vitro aggregating agents (adrenaline, adenosine diphosphate, and collagen) than platelets from healthy, moderate drinkers. Initially, platelet counts in platelet rich plasma tended to be low and the Simplate II bleeding times frequently prolonged. Platelet aggregation and thromboxane A2 release, however, were inhibited even in patients with normal platelet counts on admission. Platelet aggregation and thromboxane A2 release returned to normal or became hyper-responsive during two to three weeks of abstinence. Platelet counts rose during this period, the largest responses occurring in those patients with the lowest counts on admission. Bleeding times reverted to normal during abstinence and correlated significantly with changes in platelet aggregation, thromboxane A2 release, and platelet count and with the estimated ethanol consumption during the week before admission. Chronic, heavy alcohol ingestion evidently exerts an inhibitory effect on platelet function even in the absence of alcohol in the blood, and this phenomenon is reversible on abstaining. The impaired platelet function, together with the reduced platelet count, may contribute to the bleeding diathesis associated with chronic alcoholism and to the increased incidence and recurrence of gastrointestinal haemorrhage associated with excessive alcohol intake.

Absent ileal uptake of IF-bound vitamin B12 in vivo in the Imerslund-Grasbeck syndrome (familial vitamin B12 malabsorption with proteinuria)

A Syrian family is described with three children who had inherited selective vitamin B12 malabsorption associated with proteinuria. (Imerslund-Grasbeck syndrome). Although inherited the defect was apparently not present at birth. A third child had less severe vitamin B12 malabsorption, was not vitamin B12 deficient and had no proteinuria. Studies on two of the affected children with subcellular fractionation of the uptake of radioactive vitamin B12 by ileal tissue in vivo indicate a defect in the ileal receptors for IF-bound vitamin B12. These findings are different from the single in vitro experiment on a patient with this condition that has been previously reported.

Aldehyde dehydrogenase in alcoholic subjects

Hepatic aldehyde dehydrogenase activity is depressed in alcoholic liver disease and may account for the observation that alcoholics develop high blood acetaldehyde concentrations following ethanol. To determine whether this is a specific defect in alcoholics, aldehyde dehydrogenase was studied in liver tissue obtained from three groups of subjects. Group I comprised 30 patients with alcoholic liver disease, Group II consisted of eight subjects with liver disease unrelated to alcohol abuse and Group III was a control group of 10 individuals with no significant liver disease. Mean hepatic aldehyde dehydrogenase activity was significantly lower in Group I than in Groups II or III [4.9 +/- 0.6 (mean +/- S.E.), compared to 10.2 +/- 1.8 and 12.4 +/- 1.1 nmoles of acetaldehyde oxidized per min X mg of protein, respectively]. Aldehyde dehydrogenase activity in Group II was relatively well maintained. Aldehyde dehydrogenase activity was found in cytosolic and mitochondrial fractions of liver homogenates. In alcoholic subjects, cytosolic aldehyde dehydrogenase activity was not more depressed than was mitochondrial aldehyde dehydrogenase. Isoelectric focusing demonstrated a single mitochondrial isoenzyme and a single cytosolic isoenzyme in most cases in Group III. In contrast, multiple cytosolic isoenzymes were consistently found in liver tissue from Group I subjects. These findings suggest that depressed aldehyde dehydrogenase activity in alcoholic subjects is not a consequence of liver disease.

The preparation of human intrinsic factor-cobalamin complex from human gastric juice by immunoadsorption

Immune complexes of human intrinsic factor were prepared by mixing gastric juice saturated with vitamin B12, and sera from patients with pernicious anaemia that had a high proportion of binding (Type II) antibody. The complexes were isolated by sodium sulphate precipitation followed by Sephadex G-150 gel filtration. Acid conditions dissociated the immune complexes and allowed separation of specific antibody and purified antigen bound to vitamin B12 by Sephadex G-200 gel filtration. Specific antibody was covalently attached to Protein A Sepharose CL-4B by coupling with water soluble carbodiimide which allowed intrinsic factor-B12 complex to be purified directly from gastric juice. The intrinsic factor obtained after iodination, ran as a single band on SDS-polyacrylamide gel electrophoresis and was biologically active.

Effect of alcohol consumption on hepatic aldehyde dehydrogenase activity in alcoholic patients

Two liver biopsies were performed 6 months apart in each of 29 patients with alcoholic liver disease. Hepatic aldehyde dehydrogenase activity was measured on each occasion. The patients were seen regularly and their alcohol consumption was assessed independently. Hepatic aldehyde dehydrogenase activity was unchanged in 17 patients who continued to drink to excess; it rose in 10 patients who significantly reduced their alcohol intake; and it fell dramatically in 2 patients who were virtually abstinent initially, but then began drinking heavily. These results clearly demonstrate that alcohol consumption itself depresses hepatic aldehyde dehydrogenase activity. It is unlikely that the low hepatic aldehyde dehydrogenase activity reported in alcoholics represents a primary abnormality predisposing to alcoholism or alcoholic liver disease.

Controlled trial of propranolol for the prevention of recurrent variceal hemorrhage in patients with cirrhosis

We conducted a prospective randomized trial of propranolol for the prevention of recurrent variceal bleeding in 48 patients with cirrhosis of the liver. During a follow-up period of up to 21 months, 12 of 26 patients in the propranolol group and 11 of 22 in the control group had rebleeding from esophageal varices. There was no significant difference in rebleeding between the two groups. This contrasts with a previous report of the efficacy of propranolol in preventing recurrent gastrointestinal bleeding in alcoholic cirrhosis. The difference in results may be due to the inclusion in our study of patients with other causes of cirrhosis and more severe liver disease. Propranolol may not be indicated for the prophylaxis of variceal rebleeding in such patients, and we advocate that its use be limited at present to controlled clinical trials.

A Climatic Freshening of the Deep Atlantic North of 50 N over the Past 20 Years

Observations made in summer 1981 show a significant and widespread decrease in salinity, averaging 0.02 per mil, in deep waters of the subpolar North Atlantic over the past two decades. This implies a relatively rapid response of deep water formation to climatic perturbation.

The effect of ranitidine on the plasma clearance and hepatic extraction of indocyanine green in patients with chronic liver disease

Since hepatic clearance of ICG is reduced by H2-receptor antagonists in normal subjects, it has been suggested that they reduce liver blood flow. We have studied the effect of intravenous ranitidine on ICG clearance in twelve patients with chronic liver disease. Wedged and free hepatic venous pressure were measured before and after intravenous ranitidine in nine of the patients, and the hepatic extraction of ICG was determined in six patients. ICG clearance fell by 22 +/- 11% (s.e. mean) 60 min after ranitidine. In patients in whom ICG clearance fell after intravenous ranitidine the hepatic extraction of ICG was also reduced. There was no significant change in the gradient between wedged and free hepatic venous pressure after ranitidine. It is therefore unlikely that ranitidine lowers liver blood flow.

Subcellular localization of acetaldehyde dehydrogenase in human liver

The subcellular distribution of aldehyde dehydrogenase activity was determined in human liver biopsies by analytical sucrose density-gradient centrifugation. There was bimodal distribution of activity corresponding to mitochondrial and cytosolic localizations. At pH 9.6 cytosolic aldehyde dehydrogenase had a lower apparent Kappm for NAD (0.03 mmol l-1), than the mitochondrial enzyme (Kappm NAD = 1.1 mmol l-1). Also, the pH optimum for cytosolic aldehyde dehydrogenase activity (pH 7.5) was lower than that for the mitochondrial enzyme activity (pH 9.0), and the cytosolic enzyme activity was more sensitive to inhibition by disulfiram in vitro. Disulfiram (40 mumol l-1) caused a 70% reduction in cytosolic aldehyde dehydrogenase activity, but only a 30% reduction in mitochondrial enzyme activity after 10 min incubation. The liver cytosol may therefore be the major site of acetaldehyde oxidation in vivo in man.

Nuclear magnetic resonance (NMR) imaging in Wilson disease

Nuclear magnetic resonance (NMR) scans of the head and liver were obtained in 13 patients with Wilson disease, and the results were compared with computed tomography (CT). Twelve age and sex matched normal controls were also scanned with NMR. The subjects were scanned using repeated free induction decay (RFID), inversion-recovery (IR), and spin-echo (SE) sequences. The IR scans of the brain provided excellent anatomical localisation while SE scans highlighted pathological areas. Within the brain, NMR demonstrated abnormalities in two patients with normal CT scans. More extensive involvement was shown with NMR in three additional cases. In the liver, NMR and CT showed similar abnormalities of morphology. T1 values were within the normal range in all cases, including three patients with high liver copper levels at the time of NMR examination.

Efficacy of clonidine in treatment of alcohol withdrawal state

Clonidine hydrochloride 5 micrograms/kg and placebo were given orally to 11 patients experiencing well-developed alcohol withdrawal states. Active drug and placebo were given in a randomised, cross-over double blind fashion 2 h apart. Clonidine significantly suppressed heart rate (P = 0.002), arterial blood pressure (P = 0.006), and an accumulated score of withdrawal symptoms and signs (P = 0.004). These data suggest that clonidine may be useful in the management of alcohol withdrawal states, and that the underlying pathophysiology of at least some of these manifestations may be sympathetic nervous system hyperactivity.

Impaired acetaldehyde oxidation in alcoholics

High blood acetaldehyde levels in alcoholics after ethanol ingestion are due to reduced acetaldehyde oxidation rather than to an increased rate of its formation from ethanol. This is associated with low hepatic acetaldehyde dehydrogenase activity in alcoholic subjects and may represent a specific abnormality in them.

Guillain-Barré syndrome associated with hepatitis A in a male homosexual

A 48-year-old male homosexual developed the Guillain-Barré syndrome in association with acute hepatitis. The hepatitis A virus was almost certainly transmitted sexually. Since the incidence of viral hepatitis is high in active male homosexuals, they are particularly at risk of developing such complications.

Advection of Pore Fluids Through Sediments in the Equatorial East Pacific

Measurements of the ratio of helium-4 to helium-3 and of calcium ion in the pore waters of sediments at two locations in the eastern equatorial Pacific indicate that solution advection is occurring through the sediments. Both the helium ratio and the calcium ion profile yield velocity values for advective flow of about 20 centimeters per year. Mass balance constraints are also consistent with the interpretation presented. Flow appears to be occurring thorugh relatively thick sediments, on the order of 300 meters.

Rh(D) fraction incompatibility causing hemolytic disease of the newborn. Report of two cases in a Chinese family

Two cases of hemolytic disease of new born in a Chinese family are reported. The hemolysis was due to the production in the mother of antibodies against fractions A, C, and D of Rh(D) antigen. The fractions were absent in the mother's red blood cells which are Rh(DB) but present in her babies. Rh(DB) may be detected by the use of two types of anti-D sera, one with and the other without anti-DB activity. For transfusion purpose, all DB patients so tested, would be regarded as Rh(D) negative.

Serum glutamate dehydrogenase is not a reliable marker of liver cell necrosis in alcoholics

Serum glutamate dehydrogenase (EC 1.4.1.3.) activity was measured in 73 hospital patients who had a history of chronic alcohol abuse and who all had a liver biopsy performed. High levels of serum GDH activity occurred in those patients with recent excess alcohol consumption independently of the underlying liver histology, and did not discriminate between those patients with and those without alcoholic hepatitis.

Subcellular localisation of vitamin B12 during absorption in the guinea-pig ileum

The subcellular distribution of vitamin B12 was studied during its absorption in the guinea-pig ileum. Animals were fed either (57Co) or (58Co) cyanocobalamin and killed two or four hours later. At two hours labelled cyanocobalamin was concentrated in brush border and lysosomal fractions of ileal homogenates, with some remaining in the sample layer. In contrast, at four hours labelled cyanocobalamin was concentrated predominantly in the cytosol with much smaller peaks in the brush border and lysosomal fractions. These findings are consistent with vitamin B12 absorption by receptor-mediated endocytosis. It is suggested that, after binding at the brush border, vitamin B12 is first sequestrated within lysosomes, and then released into the cytosol, from where it leaves the cell to enter the portal blood.

Malignant epithelioma of the liver

Carcinoma complicating congenital cystic conditions of the liver is rare. The authors report a primary malignant epithelioma of the liver in association with multiple intrahepatic biliary cysts, which are not usually considered to predispose to malignancy.

Genetic factors in determining susceptibility to alcohol dependence and development of alcohol-induced liver disease

There is considerable evidence in favour of genetic factors influencing excessive drinking behaviour and development of alcohol dependence (alcoholism), although readily identified markers of these genes have not been established. In addition, environmental factors undoubtedly play an important role. Although the probability of developing a significant liver disease (alcohol-induced hepatitis with or without cirrhosis) is related to the amount of alcohol ingested, there is a great variation in susceptibility which presumably stems from either genetic or additional environmental influences. The probable linkage of development of severe alcohol-induced liver disease with alleles of the HLA-B locus would suggest the influence of a gene(s) on chromosome 6. Such a gene may determine the rate or type of metabolism of alcohol or, since the immune response genes are present on chromosome 6, may indicate genetically controlled variation in the level of the immune and inflammatory response to alcohol-induced changes in liver membrane antigenicity. Further studies are needed to confirm these associations and to determine the type of factor involved.

Selectively reduced hepatic acetaldehyde dehydrogenase in alcoholics

Acetaldehyde dehydrogenase activity in liver biopsy specimens was considerably lower in 12 non-cirrhotic alcoholics than in 11 control subjects. It is suggested that reduced enzyme activity may cause the impaired metabolism of acetaldehyde reported in alcoholics and may play a part in the pathophysiology of alcoholism. Subcellular fractionation studies showed that acetaldehyde dehydrogenase was localised in the mitochondrial and cytosolic fractions of the liver cell, but in alcoholics the cytosolic component was selectively depleted. This deficiency may be a primary defect in alcoholics, reflecting the genetic aspect of alcoholism.

Analytical subcellular fractionation of jejunal biopsy specimens: enzyme activities, organelle pathology and response to corticosteroids in patients with non-responsive coeliac disease

1. Jejunal biopsies from five patients with non-responsive coeliac disease have been subjected to analytical subcellular fractionation and enzymic microassay in order to compare the organelle pathology of this group with untreated but glutensensitive patients. 2. Compared with the gluten-sensitive group these non-responsive patients showed marked reduction of the endoplasmic reticulum enzymes, normal activities of lysosomal enzymes and slightly less severely reduced brush border activities. 3. It is suggested that the present biochemical studies in combination with previous clinical reports and measurements of DNA and protein synthesis by cultured mucosal biopsies delineate non-responsive coeliac disease as a distinct entity. 4. The patients were treated with oral prednisolone (20 mg daily) for between 5 and 9 weeks and the properties of the jejunal biopsies restudied. 5. Although morphologically there was only a partial restoration of the villus architecture the enzymic alterations and organelle abnormalities returned essentially to normal values.

Mitochondrial enzyme activities in liver biopsies from patients with alcoholic liver disease

The hypothesis that mictochondrial damage is a significant factor in the pathogenesis of alcoholic liver disease (ALD) was investigated by enzymic analysis of mitochondrial fractions isolated from needle biopsy specimens from control patients, patients with fatty liver due to chronic alcoholism, and from patients with other forms of liver disease. Enzymes associated with the inner and outer mitochondrial membranes showed normal levels in ALD. Enzymes associated with the mitochondrial matrix, glutamate dehydrogenase, malate dehydrogenase and aspartate aminotransferase showed significantly raised levels in ALD, but the levels in patients with non-alcoholic liver disease was normal. In addition, analysis of the mitochondria by sucrose density gradient centrifugation revealed no differences between control tissue and liver from patients with alcoholic liver disease. These results do not indicate that there is significant mitochondrial damage in ALD. The raised mitochondrial matrix enzymes may represent an adaptive response to the ethanol load.

Treatment of carcinoid liver metastases by hepatic-artery embolisation

Two patients with multiple hepatic carcinoid metastases experienced considerable symptomatic relief after the hepatic artery was embolised with fragments of absorbable gelatin sponge administered through a percutaneous arterial catheter. With adequate pharmacological cover the technique is a safe, effective, and relatively painless treatment for a condition which is usually very difficult to manage.

Tritium-Helium Dating in the Sargasso Sea: A Measurement of Oxygen Utilization Rates

The newly developed technique of "tritium-helium dating" has been used to investigate in situ rates of oceanic oxygen utilization. As an example, an apparent oxygen utilization rate of 0.20 +/- 0.02 milliliter per liter of water per year has been obtained for the Subtropical Mode water (18 degrees C water) in the Sargasso Sea.